The proposed and ongoing studies included in this application are for the treatment of acute leukemia and solid tumors in children. The present new patient study for acute lymphocytic leukemia divides patients by age, WBC at diagnosis, cell morphology, and the status of the CSF at diagnosis. Induction treatment is similar for all groups. Maintenance therapy is randomized within each group to two or more programs for both the CNS and systemic therapy. New patient therapy for acute non-lymphocytic leukemia includes induction with cytosine arabinoside and adriamycin. Children who enter remission will receive bone marrow transplant if a suitable sib donor is available. All others will continue on multi-drug maintenance therapy. New solid tumor studies effected within the past year include those for Wilms' tumor, Ewing's sarcoma and rhabdomyosarcoma. All of these are intergroup studies. New agents in Phase II study for leukemia and/or solid tumors include azapicyl, beta-deoxythioguanosine, prednimustine, Poly I-Poly C, and dianhydrogalactitol. Interferon is being studied in a controlled trial for the treatment of varicella in children on chemotherapy.